This disclosure pertains generally to networked communication satellite systems and in particular to an extensible high bandwidth global space communication satellite system.
Satellite constellations are used as a network of a plurality communication satellites to provide coordinated ground coverage. The plurality of networked satellites operate together under shared control and are synchronized so that their communication coverage may overlap to complement each other while minimizing interference between the satellites' coverage.
Low earth orbiting satellites (LEOs) are often deployed in satellite constellations. Because the coverage area provided by a single LEO satellite only covers a small area that moves as the satellite travels at high angular velocity needed to maintain its orbit, a plurality of LEO satellites are often needed to maintain continuous coverage over a larger area. Examples of satellite constellations include the Global Positioning System (GPS), Galileo and GLONASS constellations for navigation and geodesy, the Iridium® and Globalstar satellite telephony services, the Disaster Monitoring Constellation and RapidEye for remote sensing, the Orbcomm messaging service, Russian elliptic orbit Molniya and Tundra constellations, the large-scale Teledesic and Skybridge broadband constellation proposals of the 1990s, and the proposed LEO global backhaul constellation named COMMStellation™.
One benefit of using LEO satellites is the ability to provide low latency broadband telecommunications compared to geostationary earth orbit (GEO) satellites. Indeed, the latency of Earth-to-LEO satellite communication or LEO satellite-to-earth communication is about 1 ms to 5 ms, whereas the one-way latency of Earth-to-GEO satellite communication is about 120 ms. A LEO satellite constellation can also provide more system capacity by frequency reuse across its coverage, with spot beam frequency use being similar to the frequency reuse of cellular radio towers.
Medium Earth orbit (MEO) satellite constellations may also provide a solution for overcoming the latency challenge in GEO constellations. MEO is the region of space around the Earth above low Earth orbit (altitude of 2,000 km) and below geostationary orbit (altitude of 35,786 km). The most common use for satellites in this region is for navigation, such as the GPS Glonass, and Galileo constellations.
Presently, there are various conventional commercial type satellite communication systems. One satellite communication system intended for the internet is Teledesic which has never been fully implemented. Teledesic successfully launched only one satellite. Another satellite communication system intended for voice and data communication is Iridium® which has a total of 66 satellites. Iridium® is a LEO satellite constellation. Iridium® has low latency communication and supports inter-satellite links only between satellites orbiting in the same direction using RF based cross-links. The cross-links have a limited bandwidth capacity which can be sufficient for voice, but insufficient for real-time video feed.
GEO satellite constellations such as the European Data Relay Satellite (EDRS) system are based on geostationary earth orbit satellites which are at a higher altitude from the earth's surface. EDRS satellites relay information between satellites and ground stations. Certain GEO constellations utilize a laser cross-link to provide communication between satellites. However, due to the position of the satellites at relatively higher altitude (about 36000 km above sea level) the communication latency from a ground base station to the satellite is about 120 ms for a one-way trip. Furthermore, deploying GEO satellites is far more expensive than deploying LEO or MEO satellites.
Prior satellite communication systems have not been able to support a relatively broad communication bandwidth while providing a real-time, extendible or reconfigurable communication network.
With the increasing need for satellite communications, there is a persistent need in the art for a system and method for providing an extensible high bandwidth communication satellite network.